Hiyosu (鵯州

Hiyosu is a large, green Shinigami with a bulbous head and an extendible eyeball via a crank on his head. He was the one that originally discovered Rukia Kuchiki's unusual Gigai. Later, he is shown scolding Rin for scanning incorrectly when Soifon and Yoruichi Shihōin are investigating the Bounts. He was also present when the Research Institute discovered that Yammy Rialgo and Ulquiorra Cifer had begun a small invasion on Karakura Town.

Hiyosu, along with the other members of the Research Institute, has also been known to perform field research when requested by his captain, Mayuri Kurotsuchi, as shown during the Beast Swords arc.[1]